Roofing Calculator
You don't need to climb on the roof. Measure the house footprint from the ground and estimate the pitch. The calculator converts it to sloped roof area and a full shingle material list.
- Tested formulas
- Feet or metric
- Printable shopping list
2 What to buy
Updates as you type| Footprint incl. overhang | 1,344 sq ft |
|---|---|
| Sloped roof area | 1,503 sq ft |
| Squares (100 sq ft) with waste | 16.53 |
| Ridge / hip length | 42 ft → 2 bundles of ridge cap |
| Eaves + rakes | 156 ft → 2 starter bundles, 16 × 10 ft drip edge |
| Roofing nails | ≈ 5,440 (≈1 × coil box of 7,200) |
Shopping list
Quick answer
A 40 × 30 ft house with a 6/12 gable roof and 12-inch overhangs has about 1,503 sq ft of roof. With 10% waste that's 16.5 squares, or 50 bundles of shingles at 3 bundles per square.
Shingle bundles by house size
| House footprint | 4/12 pitch | 6/12 pitch | 8/12 pitch | 10/12 pitch |
|---|---|---|---|---|
| 40 × 25 ft (1000 sq ft) | 40 bundles | 42 bundles | 45 bundles | 49 bundles |
| 50 × 30 ft (1500 sq ft) | 58 bundles | 62 bundles | 66 bundles | 72 bundles |
| 50 × 40 ft (2000 sq ft) | 76 bundles | 81 bundles | 87 bundles | 94 bundles |
| 60 × 40 ft (2400 sq ft) | 91 bundles | 97 bundles | 104 bundles | 112 bundles |
| 70 × 40 ft (2800 sq ft) | 106 bundles | 112 bundles | 120 bundles | 130 bundles |
Gable roof, 12" overhangs, 10% waste, 3 bundles per square. Use the calculator above for your exact size.
From footprint to roof area
A sloped roof has more area than the ground it covers. Multiply the footprint (including overhangs) by the pitch factor, √(1 + (pitch ÷ 12)²). For a 6/12 roof that's 1.118, so the roof is about 12% bigger than its footprint.
| Pitch | Factor | Pitch | Factor |
|---|---|---|---|
| 3/12 | 1.031 | 8/12 | 1.202 |
| 4/12 | 1.054 | 9/12 | 1.250 |
| 5/12 | 1.083 | 10/12 | 1.302 |
| 6/12 | 1.118 | 12/12 | 1.414 |
| 7/12 | 1.158 |
Worked example: 40 × 30 ft house, 6/12 gable, 12" overhang
- Footprint with overhang: 42 × 32 = 1,344 sq ft
- × 1.118 = 1,503 sq ft of roof
- + 10% waste = 16.53 squares → 50 bundles
- 2 bundles of ridge cap, 2 of starter strip, 2 rolls of synthetic underlayment
How to find your roof pitch from the ground
From inside the attic, or on a ladder at the gable end, hold a level horizontally against a rafter. Measure 12" along the level, then measure straight up from that point to the underside of the rafter. That vertical measurement is your pitch. You can also find pitch-finder apps that use your phone's camera from the ground.
Waste factor
Simple gable roofs need about 10% extra for cuts at the rakes. Hip roofs need about 15% because every hip edge is cut. Roofs with valleys, dormers and skylights can need 18–20%. Unopened bundles can usually be returned.
Frequently asked questions
What is a roofing square?
A square is 100 square feet of roof surface. Most architectural shingles come 3 bundles to the square.
How many bundles of shingles do I need for a 2,000 sq ft house?
It depends on pitch and overhang. A 50 × 40 ft (2,000 sq ft) single-story footprint with a 6/12 pitch and 1 ft overhangs has about 2,440 sq ft of roof. With 10% waste that's about 27 squares, or 81 bundles.
Do I subtract chimneys and skylights?
Only big ones. Small openings are cancelled out by the extra waste from cutting around them.
How many bundles of shingles are in a square?
Three for most architectural and 3-tab shingles, so each bundle covers about 33⅓ sq ft. Some heavier designer shingles take four or five bundles per square; the wrapper says which.
Last reviewed 2026-10-21. See how we calculate for our sources and assumptions.